Adding and Subtracting Strategies Gr. 2This mathematical unit study was created using Smart Notebook. The unit covers ten lessons; counting on, double facts, adding three numbers, and problem solving skills. There are five lessons on adding and five lesson on subtracting. Each lesson is complete with an introduction lesson and practice page. Every page is interactive. The unit includes 24 slides, objectives, and core content standards, Also included are some great teaching tools such as snap cubes number lines, interactive counters, tables, and charts.